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Electrothermal Lifetime Prediction Of Polyimide Wire Insulation With Application To Aircraft, Peter R. Hondred, Nicola Bowler, Michael R. Kessler 2017 Iowa State University

Electrothermal Lifetime Prediction Of Polyimide Wire Insulation With Application To Aircraft, Peter R. Hondred, Nicola Bowler, Michael R. Kessler

Nicola Bowler

This work investigates the electrothermal lifetime of a commonly used polyimide wire insulation material, Kapton®, through the use of thermogravimetry (TG) and breakdown voltage testing. From TG, an isoconversional model-free kinetic evaluation was used to obtain a relationship between the activation energies of degradation for Kapton as a function of weight loss. By relating the electrical life theory and the TG theory through the model defined by Toop (IEEE Trans. Dielectr. Electr. Insul. 1971, 6, 2), the electrothermal lifetime of Kapton has been calculated for conditions of 12 and 14.7 kV over a temperature range of 250–400°C ...


Hazard Assessment Of Meteoroid Impact For The Design Of Lunar Habitats, Herta Paola Montoya, Shirley Dyke, Julio A. Ramirez, Antonio Bobet, H. Jay Melosh, Daniel Gomez 2017 Purdue University

Hazard Assessment Of Meteoroid Impact For The Design Of Lunar Habitats, Herta Paola Montoya, Shirley Dyke, Julio A. Ramirez, Antonio Bobet, H. Jay Melosh, Daniel Gomez

The Summer Undergraduate Research Fellowship (SURF) Symposium

The design of self-sustaining lunar habitats is a challenge primarily due to the Moon’s lack of atmospheric protection and hazardous environment. To assure safe habitats that will lead to further lunar and space exploration, it is necessary to assess the different hazards faced on the Moon such as meteoroid impacts, extreme temperatures, and radiation. In particular, meteoroids pose a risk to lunar structures due to their high frequency of occurrence and hypervelocity impact. Continuous meteoroid impacts can harm structural elements and vital equipment compromising the well-being of lunar inhabitants. This study is focused on the hazard conceptualization and quantification ...


Using High Resolution Images To Investigate Fatigue Crack Initiation Of Alloys At The Microstructural Level, Michael P. Reinhold, Alberto Mello, Michael Sangid 2017 Purdue University

Using High Resolution Images To Investigate Fatigue Crack Initiation Of Alloys At The Microstructural Level, Michael P. Reinhold, Alberto Mello, Michael Sangid

The Summer Undergraduate Research Fellowship (SURF) Symposium

Microstructural features within a material dictate the material’s mechanical behavior and lead to localized strains as the sample is deformed. In order to further understand structural failure, an improved understanding of how microstructural features influence failure is necessary. Fatigue is one common mode of failure for aerospace applications, and a better understanding of the conditions of crack initiation can provide information that ultimately may increase longevity of aerospace systems. This paper investigates the hypothesis that fatigue crack initiation for a cyclically loaded sample is correlated to areas of higher localized strain. The experiment was conducted using a Ti-6Al-4V sample ...


Design Of Orbital Maneuvers With Aeroassisted Cubesatellites, Stephanie Clark 2017 University of Arkansas, Fayetteville

Design Of Orbital Maneuvers With Aeroassisted Cubesatellites, Stephanie Clark

Stephanie Clark

Recent advances within the field of cube satellite technology has allowed for the possible development of a maneuver that utilizes a satellite's Low Earth Orbit (LEO) and increased atmospheric density to effectively use lift and drag to implement a noncoplanar orbital maneuver. Noncoplanar maneuvers typically require large quantities of propellant due to the large delta-v that is required. However, similar maneuvers using perturbing forces require little or no propellant to create the delta-v required. This research reported here studied on the effects of lift on orbital changes, those of noncoplanar types in particular, for small satellites without orbital maneuvering ...


Meso-Scale Imaging Of Composite Materials, Robert J. Grandin, Joseph N. Gray 2017 Iowa State University

Meso-Scale Imaging Of Composite Materials, Robert J. Grandin, Joseph N. Gray

Robert Grandin

The performance of composite materials is controlled by the interaction between the individual components as well as the mechanical characteristics of the components themselves. Geometric structure on the meso-scale, where the length-scales are of the same order as the material granularity, plays a key role in controlling material performance and having a quantitative means of characterizing this structure is crucial in developing our understanding of NDE technique signatures of early damage states. High-resolution computed tomography (HRCT) provides an imaging capability which can resolve these structures for many composite materials. Coupling HRCT with three-dimensional physics-based image processing enables quantitative characterization of ...


Implementation Of Automated 3d Defect Detection For Low Signal-To Noise Features In Nde Data, Robert J. Grandin, Joseph N. Gray 2017 Iowa State University

Implementation Of Automated 3d Defect Detection For Low Signal-To Noise Features In Nde Data, Robert J. Grandin, Joseph N. Gray

Robert Grandin

The need for robust defect detection in NDE applications requires the identification of subtle, low-contrast changes in measurement signals usually in very noisy data. Most algorithms rarely perform at the level of a human inspector and often, as data sets are now routinely 10+ Gigabytes, require laborious manual inspection. We present two automated defect segmentation methods, simple threshold and a binomial hypothesis test, and compare effectiveness of these approaches in noisy data with signal to noise ratios at 1:1. The defect-detection ability of our algorithm will be demonstrated on a 3D CT volume, UT C-scan data, magnetic particle images ...


Inversion Of Eddy Current Probe Impedance Data For Crack Reconstruction, John Bowler, D. J. Harrison, S. J. Norton 2017 University of Surrey

Inversion Of Eddy Current Probe Impedance Data For Crack Reconstruction, John Bowler, D. J. Harrison, S. J. Norton

John R. Bowler

The aim of eddy current inversion is to reconstruct an unknown flaw from probe signals measured as a function of probe position and frequency or time. In seeking the solution of an inverse problem, one can take advantage of an ability to solve forward problems by using predictions of probe signals calculated with a tentative estimate of the flaw. A well known inversion strategy adopted here for eddy current inversion, is that of varying the flaw estimate iteratively until the disparity between predicted and observed probe signals is minimized. Then the model flaw which gives the optimum predictions of the ...


Deployable Antenna For Cubesat, Mackenzie Thomas Lennon, Caleb Andrew Barber, David Matthew Galves 2017 California Polytechnic State University, San Luis Obispo

Deployable Antenna For Cubesat, Mackenzie Thomas Lennon, Caleb Andrew Barber, David Matthew Galves

Mechanical Engineering

This project is a proof-of-concept ground model of a large deployable antenna designed for the small space requirements of CubeSats. This small deployment module is designed to fit a 2 m by 1 m reflective antenna inside a storage volume of with the dimensions 20 cm by 20 cm x 40 cm. The reflector will be deployed to a parabolic shape with the goal of modeling the reflector necessary for high frequency communication. Because this module is designed as a proof-of-concept for the deployable parabolic reflector specifically, no electrical components will be incorporated and will just focus on the deployment ...


Study Of Knowledge-Based System (Kbs) And Decision Making Methodologies In Materials Selection For Lightweight Aircraft Metallic Structures, Pashupati R. Adhikari, Reza Mirshams 2017 University of North Texas

Study Of Knowledge-Based System (Kbs) And Decision Making Methodologies In Materials Selection For Lightweight Aircraft Metallic Structures, Pashupati R. Adhikari, Reza Mirshams

Journal of Applied Science & Engineering Technology

This paper presents an overview of knowledge-based system (KBS) in the context of decision making methodologies used in materials selection for the design of light weight aircraft metallic structures. Overall aircraft weight reduction means substantially less fuel consumption and better efficiency. Part of the solution to this problem is to find a way to reduce overall weight of metallic structures in the aircraft. Two distinct multiple criteria decision making (MCDM) methodologies are presented with examples featuring a set of short-listed materials suitable in the design of the structures. Pre-defined constraint values, mainly mechanical properties, are employed as relevant attributes satisfying ...


Study Of Custom Tool Control In Aviation And Aerospace And Selection Of Materials And Manufacturing Process, Ethan C. Rowley 2017 Morehead State University

Study Of Custom Tool Control In Aviation And Aerospace And Selection Of Materials And Manufacturing Process, Ethan C. Rowley

Theses and Dissertations

A thesis presented to the faculty of the College of Business and Technology at Morehead State University in partial fulfillment of the requirements for the Degree of Master of Science by Ethan C. Rowley on April 27, 2017.


Unmanned Aircraft System-Based Structural Health Monitoring, Sam Dwyer 2017 Iowa State University

Unmanned Aircraft System-Based Structural Health Monitoring, Sam Dwyer

Symposium on Undergraduate Research and Creative Expression

While many think of unmanned aerial vehicles as only serving military purposes, their scope has widened immensely over recent years into the commercial realm, and even into consumer hands. Using unmanned aircraft systems to diagnose health problems and create risk values can ensure the safety of many expensive complex engineering systems, without the intrusion of human error. Engineered systems, such as space shuttles, infrastructure, airplanes, and even the runways they sit on go through regular fatigue, and need to be health monitored to ensure their safety in continued use. To do this, we attach imaging devices to a variety of ...


Using X-Ray Micro-Ct Scanning To Characterize Cracking In Composites, Rachel Roth 2017 Iowa State University

Using X-Ray Micro-Ct Scanning To Characterize Cracking In Composites, Rachel Roth

Symposium on Undergraduate Research and Creative Expression

Fibrous composites are used throughout the aerospace industry with military, commercial, satellite, and space exploration applications. Composites are desired for their high specific strength and stiffness to weight ratios, as well as their malleability to produce aerodynamically efficient structures. We used computed tomography (CT) to investigate the structural integrity of two small rectangular carbon-fiber composite samples after each underwent unknown amounts of physical stress. Results revealed consistent cracking along the long edges and patterns of cracking through the center of one sample and virtually no cracking in the other sample. The results of this study will help to determine the ...


Analysis Of Metallic Structure With Ultrasonic Nondestructive Evaluation, Carter Sawin 2017 Iowa State University

Analysis Of Metallic Structure With Ultrasonic Nondestructive Evaluation, Carter Sawin

Symposium on Undergraduate Research and Creative Expression

From the first copper tools to modern passenger jets, metals have been the most influential material in our world since their discovery and first development over 9000 years ago. Metals both literally and figuratively support civilizations, and significant failures/defects in them can be catastrophic due to this important role. To prevent failure, engineers use imaging techniques such as Nondestructive evaluation (NDE) to find and compensate for/eliminate harmful flaws like cracks. NDE allows engineers to evaluate and test metal for defects without altering or damaging the metal being tested, and is, therefore, extremely valuable. The main purpose of this ...


Nonhomogeneous Potential And Elasticity Problems By Combined Boundary And Finite Elements, Thomas J. Rudolphi 2017 Iowa State University

Nonhomogeneous Potential And Elasticity Problems By Combined Boundary And Finite Elements, Thomas J. Rudolphi

Thomas Rudolphi

The usage of the boundary integral equation method for nonhomogeneous problems and the combination of this method with the finite element method is discussed. A formulation of the finite element method and the conversion of the direct boundary integral equations into a stiffness type of equation is reviewed for potential problems. The problems associated with corner flux discontinuities, infinite elements, and symmetrization of the stiffness matrix are discussed. An algorithm for the construction of the stiffness matrices for the more general multi-degree of freedom problem is given along with some examples.


Ultrasonic Sol-Gel Arrays For Monitoring High-Temperature Corrosion, Thomas J. Eason, Leonard J. Bond, Mark G. Lozev 2017 Iowa State University

Ultrasonic Sol-Gel Arrays For Monitoring High-Temperature Corrosion, Thomas J. Eason, Leonard J. Bond, Mark G. Lozev

Leonard J. Bond

Corrosion of oil refinery equipment operating at high temperature is a growing challenge linked to an increase in sulfur concentration and acidity within the world supply of crude oils. Improved high temperature monitoring tools are needed to continuously measure the local minimum wall thickness of steel pipe subject to non-uniform internal corrosion. Thickness measurements must be sufficiently accurate to calculate the maximum allowable stress permissible as to avoid failure. Thickness measurements must also be sufficiently reliable and precise to correlate the rate of wall-loss with process conditions as to improve future corrosion rate predictions. Permanently installed structural health monitoring (SHM ...


Ultrasonic Scattering From Ahemispherical Pit Theory And Experimentalmeasurement Precision, Thomas J. Eason, Leonard J. Bond, Mark G. Lozev 2017 Iowa State University

Ultrasonic Scattering From Ahemispherical Pit Theory And Experimentalmeasurement Precision, Thomas J. Eason, Leonard J. Bond, Mark G. Lozev

Leonard J. Bond

The accuracy and precision of ultrasonic thickness measurement systems are influenced by systematic and environmental factors including the back-wall reflection surface profile. The scattering amplitude from a relatively flat and smooth back-wall surface can be characterized by the acoustic impedance ratio of the two materials at the interface. If the back-wall surface increases in roughness due to internal corrosion, then the arrival time of the incident wave upon the various surface heights will be slightly different, resulting in slight phase changes within the reflected field. In addition, the roughness of the internal surface will result in various impingement anglesrelative to ...


Boundary Element Solutions To Wave Scattering By Surface Irregularities On A Fluid-Solid Interface, S. Shenoy, Thomas J. Rudolphi, F. J. Rizzo 2017 Iowa State University

Boundary Element Solutions To Wave Scattering By Surface Irregularities On A Fluid-Solid Interface, S. Shenoy, Thomas J. Rudolphi, F. J. Rizzo

Thomas Rudolphi

The boundary element method is used to solve fluid-solid half-space problems with fluid-filled dimples and air bubbles on the solid surface. The problems, formulated in the Fourier (frequency) domain, are described by the fullspace three-dimensional acoustic and elastodynamic boundary integral equations (BIE), with pressure and displacement serving as primary variables. The techniques developed are general and may be with any kind of incident wave, however, plane waves are used in all numerical experiments. The equations governing the acoustic region are first converted mathematically to equations like those of an elastic region. The two regions are coupled and solved for the ...


A General Algorithm For The Numerical Solution Of Hypersingular Boundary Integral Equations, Massimo Guiggiani, Geeta Krishnasamy, Thomas J. Rudolphi, F. J. Rizzo 2017 Università di Pisa

A General Algorithm For The Numerical Solution Of Hypersingular Boundary Integral Equations, Massimo Guiggiani, Geeta Krishnasamy, Thomas J. Rudolphi, F. J. Rizzo

Thomas Rudolphi

The limiting process that leads to the formulation of hypersingular boundary integral equations is first discussed in detail. It is shown that boundary integral equations with hypersingular kernels are perfectly meaningful even at non-smooth boundary points, and that special interpretations of the integrals involved are not necessary. Careful analysis of the limiting process has also strong relevance for the development of an appropriate numerical algorithm. In the second part, a new general method for the evaluation of hypersingular surface integrals in the boundary element method (BEM) is presented. The proposed method can be systematically applied in any BEM analysis, either ...


Acoustic Scattering By Submerged Elastic Bodies: A Boundary Element Approach, Pratik Pran Goswami, Thomas J. Rudolphi, F. J. Rizzo, D. J. Shippy 2017 Iowa State University

Acoustic Scattering By Submerged Elastic Bodies: A Boundary Element Approach, Pratik Pran Goswami, Thomas J. Rudolphi, F. J. Rizzo, D. J. Shippy

Thomas Rudolphi

The scattering of time-harmonic acoustic waves from an elastic solid immersed in a fluid with the transmission of elastic waves into the solid is a generic problem of interest to various disciplines. A solution strategy for this class of problems is of direct significance to the NDE community, where such knowledge can contribute to a simulation scheme for an ultrasonic immersion scanning system with randomly distributed, subsurface flaws. Use of the boundary element method (BEM) is known to be an effective tool in handling such scattering problems, especially in the mid range frequencies where asymptotic approximations fail. The strength of ...


Elastic Wave Scattering By Arbitrarily Shaped Voids, Paul J. Schafbuch`, R. Bruce Thompson, F. J. Rizzo, Thomas J. Rudolphi 2017 Iowa State University

Elastic Wave Scattering By Arbitrarily Shaped Voids, Paul J. Schafbuch`, R. Bruce Thompson, F. J. Rizzo, Thomas J. Rudolphi

Thomas Rudolphi

This work is motivated by the need for realistic ultrasonic probability of detection (POD) models in nondestructive evaluation (NDE). Past POD models have utilized flaw farfield scattering amplitudes along with other system parameters to predict the expected signal in postulated measurement geometries [1]. However, numerical evaluations of scattering amplitudes have generally been restricted to idealized flaw shapes and, to our knowledge, no scheme to calculate scattering amplitudes of arbitrary shape has ever been implemented in 3D. Volumetric shapes with an axis of symmetry have been examined with T-matrix and MOOT [2,3] but the axisyrametric limitation precludes a large portion ...


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